Sarah R. Catalano

Parasites as biological tags to assess host population structure: guidelines, recent genetic advances and comments on a holistic approach

Graphical abstract Hundreds of dicyemid parasites (white, fuzzy strands) attached to the renal appendage (in red) of a cuttlefish individual.

Redescriptions of two species of microcotylid monogeneans from three arripid hosts in southern Australian waters

Microcotyle arripis Sandars, 1945 is redescribed from Arripis georgianus from four localities: Spencer Gulf, Gulf St. Vincent, off Kangaroo Island and Coffin Bay, South Australia, Australia. Kahawaia truttae (Dillon & Hargis, 1965) Lebedev, 1969 is reported from A. trutta off Bermagui, New South Wales and is redescribed from a new host, A. truttaceus, from four localities in South Australian waters: Spencer Gulf, Gulf St. Vincent, off Kangaroo Island and Coffin Bay. Phylogenetic analysis of the partial 28S ribosomal RNA gene (28S rRNA) nucleotide sequences for both microcotylid species and comparison with other available sequence data for microcotylid species across four genera contributes to our understanding of relationships in this monogenean family.

Revision of the water-holding frogs, Cyclorana platycephala (Anura: Hylidae), from arid Australia, including a description of a new species.

The water-holding frog, Cyclorana platycephala, occurs in the Australian arid and semi-arid zones but not in the central Australian deserts. Recent inspection of morphological variation in adults and larvae suggests that the taxon comprises three regional populations: eastern, northern and western that may each represent separate species. To assess the systematic status of these populations, we documented phylogenetic relationships using mitochondrial and nuclear DNA markers, divergence in adult and larval morphology and male advertisement call. Our molecular genetic data demonstrates that the western population of C. platycephala is not the sister taxon of eastern and northern representatives of this nominate species, as the latter two are more closely related to another morphologically distinct species, C. verrucosa. Discriminant Function Analysis of 14 morphological traits in adults and 15 in larvae showed a high degree of morphological differentiation of western versus eastern/northern C. platycephala. Calls of eastern and western populations differed in duration, pulse rate, frequency and especially in amplitude modulation pattern across the call duration. We describe the western population as a new species, whose range is contained entirely within Western Australia. In addition, we redescribe Cyclorana platycephala, quantify morphological and genetic differences between the eastern and northern populations, and conclude that these data support recognition of a single species, Cyclorana platycephala, for populations found in New South Wales, the Barkly Tablelands and south-eastern Northern Territory, Queensland and South Australia.

The value of host and parasite identification for arripid fish

Accurate identification of fishes and their parasites is fundamental to the development, management and sustainability of fisheries and aquaculture worldwide. We examined three commercially and recreationally exploited Australian arripid species (Pisces: Arripidae), namely Australian herring (Arripis georgianus), eastern Australian salmon (A. trutta) and western Australian salmon (A. truttaceus), to determine their metazoan parasite assemblages and infection parameters. We identified 49 parasite species including 35 new parasite–host records and recognised seven ambiguous parasite–host records in the literature, largely a consequence of unsubstantiated host identifications in previous studies. Morphological and molecular methods confirmed a new western extension for the range of A. trutta, ~1000 km west of the previous record. Confusion about host identification and the range extension documented here has implications for the management of these economically important arripid species in southern Australian waters. Our examination of an endemic Australian fish family emphasises that accurate identification of fishes and their parasites is a fundamental pre-requisite for efficient and sustainable resource management.

Using the giant Australian cuttlefish (Sepia apama) mass breeding aggregation to explore the life cycle of dicyemid parasites

Dicyemid mesozoan parasites, microscopic organisms found with high intensities in the renal appendages of benthic cephalopods, have a complex, partially unknown life cycle. It is uncertain at which host life cycle stage (i.e. eggs, juvenile, adult) new infection by the dispersive infusoriform embryo occurs. As adult cephalopods have a short lifespan and die shortly after reproducing only once, and juveniles are fast-moving, we hypothesize that the eggs are the life cycle stage where new infection occurs. Eggs are abundant and sessile, allowing a huge number of new individuals to be infected with low energy costs, and they also provide dicyemids with the maximum amount of time for survival compared with infection of juvenile and adult stages. In our study we collected giant Australian cuttlefish (Sepia apama) eggs at different stages of development and filtered seawater samples from the S. apama mass breeding aggregation area in South Australia, Australia, and tested these samples for the presence of dicyemid DNA. We did not recover dicyemid parasite cytochrome c oxidase subunit I (COI) nucleotide sequences from any of the samples, suggesting eggs are not the stage where new infection occurs. To resolve this unknown in the dicyemid life cycle, we believe experimental infection is needed.